About ice particles and climate change: research in the cloud chamber


Kristina Höhler could also store corona vaccines in the cloud chamber. The three-story high system of the Karlsruhe Institute of Technology (KIT) can be cooled down to minus 90 degrees. “Usually we only cool them to minus 20, minus 30 degrees,” says Höhler. The chemist and her colleagues at the Institute for Meteorology and Climate Research are less interested in vaccines – they are more interested in how clouds form.

Sounds simple. But even though clouds have been hovering across the sky for millions of years, many questions remain unanswered. Among other things, it is about the formation of clouds and their influence on the climate. “In particular, the formation of ice particles in the atmosphere is not yet sufficiently well understood,” explains Axel Seifert from the German Weather Service (DWD). For example, it is about the effect of the aerosol particles as ice nuclei. It has been investigated for many years. However, the progress is extremely slow, since it is difficult and complicated phenomena, “which also push the experimenters to their limits”.

Such aerosol cloud processes the KIT researchers investigate in the Aida cloud simulation chamber, which is unique in Germany. More than 80 cubic meters of air fit in there, the walls are covered with ice, as Höhler explains. Then, for example, desert sand is introduced and the pressure is lowered. This would also reduce the temperature and the researchers could observe the formation of clouds – and above all measure them. Unlike in nature, there are no fine dust, pollen or other particles buzzing around. “That is a clear advantage if you don’t always have to examine everything at once,” says Höhler.

The researchers are investigating how clouds influence the climate in the AIDA cloud simulation chamber at KIT.

(Image: Markus Breig)

Together with her colleague Ottmar Möhler, she heads a newly established CIS center, in which researchers from Leipzig, Great Britain and Austria are also involved. It’s part of one Europe-wide project Actris for long-term observation of aerosols, clouds and trace gases.

It should start in the course of this year. Then the scientists want to measure various cloud variables such as liquid content, the number and size of ice crystals and the chemical composition of cloud water, as Höhler says. The focus is particularly on the so-called ice-nucleating particles (the word comes from the Latin term nucleus for core). Because even when it is minus 20 degrees high up in the sky, ice does not automatically form, explains the chemist.

The preparations are scheduled for five years, as Höhler says. Among other things, it is planned to set up national measuring stations as widely as possible. Mobile platforms should also be flown in clouds with drones. Actris itself should then run for at least 20 years. According to a spokesman, the Federal Ministry of Research is still talking to the Ministry of the Environment about the extent to which the project is being funded. The federal government expects from Actris “that the factual basis for political decisions, especially on climate change, air quality and long-distance transport of air pollutants, will be significantly improved”. In this way, Actris will also contribute to the implementation of the Paris Agreement and the European and German climate goals as well as the sustainability goals, the spokesman said.

Clouds transport water, reflect sunlight, but also prevent heat from being dissipated into space. The number of their particles and the ratio of water droplets and ice in them vary. Globally rising temperatures can, for example, result in clouds being formed at different altitudes or in less or more cloud ice. “If glaciers recede in Iceland, we will have more dust particles in the air,” says Höhler. If other plants grow in regions due to higher temperatures, there are other inputs into the air. All of this has an impact on clouds – and these in turn on the climate. “We expect a change in cloud formation, which will have an impact on climate change.”